The present invention relates in general to waste water treatment, and in particular to a device for purification of waste water by oxidizing waste water constituents, at normal pressure and at ambient temperature by oxygen containing gases or oxygen in the presence of solid catalytic particles. The device is of the type which includes a reaction vessel which is provided with feeding means for the waste water, with discharging means for the purified water, and with an aerating device.
From the German Patent No. 2 050 874 a method is known applicable for purifying waste water contaminated with emulsified and dissolved oxidizable organic and inorganic substances. In this known method, waste water to be treated is mixed with air in the presence of active carbon or ion-exchange catalyzer, and the oxidizable substances contained in the waste water are disintegrated by the resulting catalytic oxidizing reaction at normal pressure and ambient temperature, that is, at about 1 bar and about 5.degree.-50.degree. C. This prior-art purifying method is carried out in a reaction chamber charged with the catalyzer; aerating nozzles through which acid-containing gases are injected into the waste water being arranged in the bottom of the chamber. Waste water to be treated is continuously fed in the reaction chamber and so is removed the purified water. Catalytic particles are kept in suspension and whirled by streams of the waste water and the applied air, so that sufficiently large catalytic surface is always available for the reaction participants. It has also been devised to provide the reaction chamber with a stirring apparatus or agitator or with a circulating pump, so as to accelerate the catalytic oxidation reaction.
The prior-art reaction chamber, however, has the disadvantage that, in order to maintain the whirling or fluidized bed of the catalyzer, considerable amounts of energy supplied by the air stream are necessary. For example, about 5 cubic meters air for 1 cubic meter of the aerating space is required. In addition, due to such a violent air stream, a certain part of the catalyzer is comminuted in an undesirable manner. It is true that, by employing agitators, the amount of air for maintaining the whirling bed of catalyzer could be reduced, but the abrasion of the catalytic particles would remain the same. Also, the application of a circulation pump for the catalyzer-waste water mixture for producing the whirling bed of catalyzer has proved to be disadvantageous, inasmuch as the abrasion of the catalyzer is excessively large. Moreover, energy spent by agitators and pumps frequently exceed the energy saved by diminishing the amount of air.
The reaction vessel employed in the prior-art methods is in the form of so-called double-pool vessels consisting of two mirror-symmetrically arranged basins, the separating central wall having no feed-in and discharge devices. Water under treatment overflows this central partition. In the main streaming direction, it is in the range of the central partition, a deviating guide is provided which is supposed to generate a vertical circulating stream. The disadvantage of this known reaction vessel configuration, apart from the limits imposed on the width of the vessel, is the fact that the catalyst or contact particles, which for example in the case of overload of the reaction vessel are displaced in the streaming direction over the central partition, are not returned against this stream direction. In the case of different distribution of the air stream, the contact agent is conveyed in the direction toward the smaller air jet, and consequently considerable irregularities in the catalyst distribution will result. The catalyst particles deposit in a completely unorderly manner in the vessel and are either completely lost for use in the whirling bed or obstruct at the points of deposition the discharge of air.
It is possible to feed back the thus deposited catalyst particles by means of mechanical devices such as grippers or pumps of special construction; nevertheless, such measures are complicated, costly and frequently unusable in practice. In order to avoid the disadvantages mentioned above, a reaction vessel has been devised in which air pressure streaming was generated. This solution, however, resulted in a unilateral displacement of the contact particles and obstructed the circulation.